Tree species identity alters forest litter decomposition through long‐term plant and soil interactions in Patagonia, Argentina

Abstract

Summary 1.A major challenge in predicting biodiversity effects on ecosystem functioning is to understand the linkages between above-ground and below-ground components in natural communities. However, incongruities in spatial and temporal scale between plant and soil processes, and confounding ecological factors, have impeded our understanding of biodiversity effects on below-ground processes, particularly in natural ecosystems with long-lived species such as forests. 2.We designed an approach to isolate plant species composition effects from other ecosystem factors, in order to evaluate the effects of individual tree species and tree species mixtures on litter decomposition in a mixed old-growth forest in temperate South America. We identified 'tree triangles' where the intersection of plant canopies directly controlled micro-environmental and biogeochemical conditions on the forest floor. The monospecific treatment included triangles composed of three trees of a single species of Nothofagus dombeyi , N. obliqua or N. nervosa , while the mixed-species triangles consisted in the intersections of the three different Nothofagus species. 3. We placed litterbags with N. dombeyi , N. obliqua or N. nervosa litter and mixed litter of the three species within all these triangles and estimated the decomposition constant ( k ) after 1 year of incubation. We also used a standard litter type in all triangles to independently evaluate the tree triangle effects on decomposition. 4. We found that plant species affected decomposition through both direct and indirect effects. Direct effects were mediated through leaf litter quality, while indirect effects were related to unique conditions that the plant species created in the surrounding environment. Despite litter decomposition variation among triangles, standard soil biogeochemical conditions such as soil C : N ratios, microbial biomass and pH were similar among microsites. 5. Most interestingly, we explicitly demonstrated that long-term effects of plant species created specific conditions that enhanced decomposition of their own litter, establishing affinity effects between single-species litter and their own microenvironment. 6. Synthesis. Our results highlight that plant species identity and long-term plant-soil feedbacks are important in affecting litter decomposition in this temperate Patagonian forest. Thus, changes or losses in temperate forest above-ground biodiversity can directly impact litter decomposition both through changes in litter quality inputs and, additionally, through the loss of specific plantsoil interactions that affect below-ground processes.

Photodegradation alleviates the lignin bottleneck for carbon turnover in terrestrial ecosystems

“…We collected senescent leaf material from 23 species across a range of life forms, families, and functional types from temperate ecosystems of South America (Table S1). Leaf litter came from the Pampas grassland region of central Argentina (native mixed C 3 -C 4 prairie and agroecosystems) (50), the Patagonian semiarid steppe (51), and temperate mixed deciduous-evergreen forest (52). All leaf litter was carefully collected from the field sites at the natural time of senescence or, in the case of evergreen species, brought to the laboratory and separated for only recently senesced, fully intact litter.…”

“…Absorbance was measured at λ = 760 nm. For quantification, a calibration curve was made using gallic acid (0.1 mg/L) as a standard (52). Sunscreens present in plant litter were measured using a methanol extraction (53).…”

La deposición de cenizas volcánicas modula la descomposición de hojarasca en bosques de Nothofagus dombeyi del norte de Patagonia

“…Sin embargo, la descomposición de las tres posiciones fue más rápida en las parcelas de N. dombeyi sin historia de ganadería que en las parcelas con pastoreo histórico de vacunos. Pese a los efectos de la erupción volcánica en otros procesos, como el crecimiento radial de árboles, la caída de productividad foliar y de la herbivoría del dosel (Chaneton et al 2014;Magnin et al 2016), la descomposición de la broza se mantuvo en valores comparables a los registrados en bosques sin influencia de cenizas (Vivanco and Austin 2008;Oleiro 2015). Además, la descomposición en suelos enterrados por cenizas fue equivalente a la descomposición sobre el suelo donde se retiró manualmente la capa de cenizas.…”

“…A escala regional, incluyendo bosques de coihue con diferentes ambientes húmedos y secos (1500-2800 mm/año) (Piazza 2016), la descomposición promedio fue de 34±2%. Previo a la erupción del volcán, en el Parque Nacional Lanín se observó una descomposición anual de coihue alrededor de 33% (Vivanco and Austin 2008) y 20% en bosques de la VIII región de Chile (Decker and Boerner 2006); en ambos casos, para bosques situados a mayor elevación y en áreas más secas que nuestros sitios. Además, en un bosque de N. pumilio (Paso Córdoba, 800 mm/año) la descomposición fue más lenta bajo las cenizas respecto a valores previos a la erupción del CVPCC (Oleiro 2015).…”

Effect of Litter Quality on Leaf-Litter Decomposition in the Context of Home-Field Advantage and Non-Additive Effects in Temperate Forests in China

“…Knowledge of HFA for decomposition has rarely been explored. And the relative importance of litter quality remains unclear versus the effect of the forest floor environment on decomposition [18].…”